Some doubts regarding domains

Hi there ,
My doubts aren't like , how do I transfer this to that? , My doubts are more like ,
Okay , I don't think I can explain it normally , so I guess I'll try explaining it using a example ,
For instance ,
This is my forum , http://www.art-castle.biz , as you can see it already has a .biz , domain.
And what if I receive a different domain name from somewhere else , and yes , it'd be mine ,
let's say it'd be somrandomsite.net , okay , so let's say I got this domain & it's registered for a year, and I'm the owner of it , BUT , what If I wanna transfer the somerandomsite.net domain to my forum to http://www.art-castle.biz ?

To make it more easier to understand ,
Let's say my original forum , http://www.art-castle.biz , has only 150 days left till , the domain name expires , and I've received a domain name BUT it's not of the original forum , and is a different domain name , ex- somerandomsite.net , and has it's whole 365 days left till it expires (A Year , I suppose?) , So NOW , would it be possible to send the 365 days of that different domain (Which is mine , obviously.) , to my original forum , that is http://www.art-castle.biz ?
And make the amount of 150 days, till the domain expires to 515 by adding the different domain?

If I'm not understandable , then please do tell me , so that I could explain it a bit further.
Thanks in advance

Well, u r , but first, is the second domain in forumotion or not?!

Umm , wait a second , I don't get it?
Anyway , The second domain is been booked through godaddy , that should explain it a bit more?

Hello,

I'm sorry but it's not possible to merge the remaining days of domains.
It's also only possible to have 1 domain active at any one time (excluding the Subdomain - Thats the freeby one u got at making your forum)

Ah , that makes sense , so umm , what if the 150 days are over?
I mean , if they're done , Would I be able to add the domain bought from godaddy?

Yes, indeed you will be able to.
You could add any domain you wish

Ah , that helped , thanks